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Updated nbodies. Fixed sum/product on floats.

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This commit is contained in:
Christoffer Lerno
2022-12-30 02:41:17 +01:00
parent bf222557fb
commit 23a78a9ae5
4 changed files with 15 additions and 13 deletions
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19
resources/examples/nbodies.c3
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@@ -1,4 +1,6 @@
module nbodies;
import std::io;
import std::math;
const PI = 3.141592653589793;
const SOLAR_MASS = 4 * PI * PI;
@@ -24,7 +26,7 @@ fn void advance(Planet[] bodies) @noinline
double dx = b.x - b2.x;
double dy = b.y - b2.y;
double dz = b.z - b2.z;
double inv_distance = 1.0/sqrt(dx * dx + dy * dy + dz * dz);
double inv_distance = 1.0 / math::sqrt(dx * dx + dy * dy + dz * dz);
double mag = inv_distance * inv_distance * inv_distance;
b.vx -= dx * b2.mass * mag;
b.vy -= dy * b2.mass * mag;
@@ -56,7 +58,7 @@ fn double energy(Planet[] bodies)
double dx = b.x - b2.x;
double dy = b.y - b2.y;
double dz = b.z - b2.z;
double distance = sqrt(dx * dx + dy * dy + dz * dz);
double distance = math::sqrt(dx * dx + dy * dy + dz * dz);
e -= (b.mass * b2.mass) / distance;
}
}
@@ -139,23 +141,20 @@ fn void scale_bodies(Planet[] bodies, double scale)
}
}
extern fn int atoi(char *s);
extern fn int printf(char *s, ...);
extern fn double sqrt(double);
fn int main(int argc, char ** argv)
fn void main(char[][] args)
{
int n = atoi(argv[1]);
int n = args.len < 2 ? 50000000 : str::to_int(args[1])!!;
Planet[] bodies = &planet_bodies;
offset_momentum(bodies);
printf ("%.9f\n", energy(bodies));
double start = energy(bodies);
scale_bodies(bodies, DT);
for (int i = 1; i <= n; i++)
{
advance(bodies);
}
scale_bodies(bodies, RECIP_DT);
printf ("%.9f\n", energy(bodies));
return 0;
io::printfln("%.9f", start);
io::printfln("%.9f", energy(bodies));
}